1. Field of the Invention
The present invention relates to a method of manufacturing a display device having a light emitting element. The present invention further relates to a manufacturing apparatus for a display device.
2. Description of Related Art
In recent years, a display device using a light emitting element, which is represented by an electro-luminescence (EL) element and the like, has been researched and developed as substitute for a liquid crystal display device. The display device has such advantages as high definition, wide viewing angle, thinness, and lightness because of the self-luminous type. By making use of these benefits, the display device has been expected to be applied to various fields. The light emitting element has a structure in which one layer or a plurality of layers composed of various materials (hereinafter referred to as an electro-luminescent layer) is interposed between a pair of electrodes.
FIG. 11A shows a cross sectional structure of a light emitting layer 22 in which an electro-luminescent layer 11 is interposed between an anode 10 and a cathode 12. The light emitting element 22 has four short-circuit portions 13 to 16. In the short-circuit portions 13 and 14, the anode 10 is shorted to the cathode 12 since an extraneous substance (waste) 17 is adhered to the anode 10. In the short-circuit portion 15, the anode 10 is shorted to the cathode 12 since a pin hole is formed in the electro-luminescent layer 11 due to the formation of a microscopic projection in the anode 10 when the anode is formed. In the short-circuit portion 16, the anode 10 is shorted to the cathode 12 since a pin hole is caused in the electro-luminescent layer 11 due to an uneven surface of the electro-luminescent layer 11.
FIGS. 11B and 11C are top views of a pixel portion 102, wherein a plurality of pixels 101, each of which includes a light emitting element 22, is arranged in matrix. When the short-circuit portions 15 and 16 are formed in several pixels 101 or the extraneous substance 17 is adhered to several pixels 101 in the pixel portion 102 as shown in the drawings, the short-circuit portions are formed between the anode and the cathode such that a current path 24 is formed in each short-circuit portion as illustrated an equivalent circuit diagram of FIG. 11D. In the pixels where such defects are caused, light emission and non-light emission of the pixels are not carried out according to signals. Accordingly, a phenomenon in which an entire device does not emit light since almost all the electric current flows through the short-circuit portions can be caused. Or, a phenomenon in which light emission or non-light emission of a certain pixel is not performed can be caused. These phenomena result in a problem, in which images are not favorably displayed. Therefore, there is a method of manufacturing and repairing a display device, which can display images favorably (see patent document 1). [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-190390
The light emitting element is deteriorated due to various factors. As substances for promoting the deterioration of the light emitting element, for example, moisture is cited. In order to prevent the moisture from intruding into the light emitting element, a sealing treatment is generally carried out to the light emitting element under an inert gas atmosphere.